Contactors are unintelligent devices designed to switch randomly with respect to the alternating current (AC) wave pattern based on the point in time the contactor connects or disconnects the electrical flow. Typically, three poles are mated together into a contactor, one for each phase of the three-phase alternating current. At the point where the electrical coil driving a contactor is deenergized and the contactor is disconnected, each pole of the contactor disconnects effectively simultaneously, but randomly with respect to the three different electrical phases operating one hundred twenty degrees out of synchronization from the other two phases. This behavior is repeated when the electrical coil driving the contactor is energized and the contactor is connected and each pole of the contactor connects effectively simultaneously, but once again randomly with respect to the three different electrical phases.
An improvement to this technology involves smart devices that disconnect when the electrical voltage reaches a minimum value. The method of determining the minimum value varies from monitoring the voltage of the wave forms to determine a minimum average value as in the point on wave (POW) technology or by electronic devices that can only disconnect when the voltage is at a low value. These technologies require complicated systems to make the determination of when the voltage is at a low value and consequently are expensive to implement and difficult to control. Consequently these devices are only suited for large devices on large applications.
Market pressure to provide contactors capable of longer operational life and lower probability of damage to equipment powered through contactors has led to a desire for improved contactor operational design. The market is demanding a better balance between the random operational characteristics of the unintelligent contactor design and the complicated and expensive point on wave technology that currently controls all three phases of the alternating current supply. Additionally, increasing market pressure is directed at providing point on wave type control of contactors to smaller devices because of the benefits realized in the larger devices and applications.